There have been known various configurations in terms of which observation to use for positioning and how to integrate the observations for positioning in a satellite navigation/dead-reckoning navigation integrated positioning device (hereinafter, referred to as “GPS/DR integrated positioning device”) in which an observation (hereinafter, referred to as “GPS observation”) obtained from a GPS positioning system, for example, as a non-autonomous system, and an observation (hereinafter, referred to as “DR observation”) obtained from a dead-reckoning navigation system (DR: dead-reckoning navigation system), as an autonomous system, are integrated (for example, see Patent Documents 1 and 2).
Which type of configuration is employed in order to integrate the GPS observation and the DR observation largely depends on the cost of the device, required accuracy and the like. FIG. 1 is a block diagram of a typical example of the aforementioned integration type.
FIG. 1(A) shows a loosely-coupled approach, and FIG. 1(B) shows a tightly-coupled approach and a deeply-coupled approach.
In FIG. 1(A), a tracking processing module 11 tracks a phase of a GPS positioning signal of a baseband obtained by receiving a signal from a GPS satellite, and finds a position, a velocity, and the like of each satellite. A GPS positioning calculation module 12 finds a position and a velocity at a receiving point based on a pseudo range (PR), a Doppler frequency observation and the position and velocity of each satellite found by the tracking processing module 11. A DR positioning calculation module 13 finds the position and velocity based on external support data of an inertial sensor and the like. Then, an integrated positioning calculation module 14 integrates the GPS observation, such as the position and velocity obtained by the GPS positioning calculation module 12 and the DR observation, such as the position and velocity obtained by the DR positioning calculation module 13 to provide the position and velocity of higher quality to a user.
In FIG. 1(B), a tracking processing module 21 tracks a phase of a GPS positioning signal of a baseband obtained by receiving a signal from a GPS satellite, and finds a position, a velocity, and the like of each satellite. In the case of the tightly-coupled approach, an integrated positioning calculation module 22 integrates a pseudo range and a Doppler frequency obtained by the tracking processing module 21 as the GPS observation and an external support data of the inertial sensor and the like as the DR observation in one integrated positioning calculation module 22 to provide the position and velocity of higher quality to a user.
In the case of the deeply-coupled approach, the integrated positioning calculation module 22 uses a baseband complex signal (I, Q) obtained by the tracking processing module 21 as the GPS observation and an external support data of the inertial sensor as the DR observation to perform an integrated positioning calculation.
Note that the GPS positioning calculation module 12 and the integrated positioning calculation module 14 of the loosely-coupled approach and the integrated positioning calculation module 22 of the tightly/deeply-coupled approach are also referred to as a “navigation filter” in which usually the position and position error, the velocity and velocity error, inertial sensor error and the like are estimated by a Kalman filter, and the estimated respective errors are negatively fed back as a correction amount to a certain portion to be corrected.
In PNDs (Portable Navigation Devices) for personal and vehicle use, which have attracted attention in recent years, lower price and higher accuracy are required. For this reason, as disclosed in Patent Documents 1 and 2, being used is a device which integrates the external support data of a low-price inertial sensor (such as a gyroscope and an acceleration sensor), map data and the like, and the GPS observation using the loosely-coupled approach or the tightly-coupled approach.
Patent Document 1: JP 2007-93483(A)
Patent Document 2: U.S. Pat. No. 6,643,587